The present invention relates to a holographic stereogram forming apparatus which enables three-dimensional recognition of photographed images, computer-produced images and the like.
A holographic stereogram is formed by a method in which a multiplicity of images obtained by sequentially photographing a subject from different observation points are prepared as original images, and these images are sequentially recorded on a single hologram recording medium as paper tables-like or dot form elementary holograms.
For example, in a holographic stereogram having parallax information only in a horizontal direction, a plurality of original images obtained by sequentially photographing a subject from different observation points in the horizontal direction are sequentially recorded on a hologram recording medium as paper tablet-like elementary holograms.
When the holographic stereogram is viewed from a certain position by one eye, a two-dimensional image consisting of a collection of image information of parts of the individual elementary holograms is seen, and, when the position of the eye is moved in a horizontal direction, a two-dimensional image consisting of a collection of image information of other parts of the individual elementary holograms is seen. Therefore, when an observer looks at the holographic stereogram by both his eyes, slightly different two-dimensional images are seen to the left and right eyes, since the positions of the left and right eyes are slightly different in the horizontal direction.
Meanwhile, in the formation of the holographic stereogram, the individual elementary holograms are each formed through the process in which a laser beam with good coherence is branched into two beams, one of the beams is condensed on the hologram recording medium having a photosensitive material as a recording material as a projection image (object beam) modulated according to a two-dimensional image by image display means (for example, a liquid crystal panel), while the other of the beams is condensed on the hologram recording medium as a reference beam, and an interference fringe is recorded on the hologram recording medium as variations in refractive index of the photosensitive material.
In this instance, in the case of a reflection type hologram, a diffuser plate (one-dimensional diffuser plate) may be disposed in front of the hologram recording medium in order to cope with the movement of the visual point in the vertical direction (non-parallactic direction) (in order to secure the angle of visibility in the non-parallactic direction) (see, for example, Japanese Patent Laid-open No. Hei 10-20747).
In the case where the one-dimensional diffuser plate is thus arranged in front of the hologram recording medium, blurring may be generated in the non-parallactic direction, due to the difference in focus between the parallactic direction and the non-parallactic direction.